The invention relates to drilling fluid and, more particularly, to drilling fluids including a circulation loss reducing additive package which is particularly useful in high permeability reservoirs and the like.
When drilling through highly permeable, unconsolidated or micro-fractured formations, for example while drilling wells to hydrocarbon-bearing subterranean formations and the like, fluid is circulated through the hole to lubricate the drill bit, remove cuttings from the bottom of the hole, control pressure within the hole and for other reasons.
Unfortunately, highly permeable, unconsolidated or micro-fractured formations allow flow of the drilling fluid to leave the hole, which is called lost circulation. This fluid loss into the formations through which the hole is being drilled results in extra cost due to the need for constantly replacing the fluid, and further can result in damage to potentially valuable and hydrocarbon bearing formations.
It is clear that the need remains, therefore, for drilling fluids that can be used in highly permeable, unconsolidated or micro-fractured formations and the like, without substantial circulation losses.
It is therefore the primary object of the present invention to provide such a drilling fluid.
Other objects and advantages of the present invention will appear hereinbelow.